(Reviewed on 1/24/2005)
Your question is more complicated than you may suppose. The test you're considering, an electron beam computed tomography (EBCT), reveals calcium deposits in artery walls. (These deposits come from inflammation, not from the calcium in your diet or from supplements. In fact, higher calcium intake may decrease your heart attack risk.) These deposits are risk factors for heart attack and stroke. The more the scan finds, the higher your risk.
One study was published in the May 13, 2003 issue of Circulation: Journal of the American Heart Association. Between January 1993 and December 1995 researchers at the University of Illinois College of Medicine in Chicago studied 5,635 self-referred men and women, none of whom had any symptoms of heart disease. The idea was to find out if the EBCT scans could predict heart problems among this group. Some of the participants had risk factors for heart disease including high blood pressure or high cholesterol.
In the three and a half years after having the scan, 224 of the participants needed heart bypass surgery; angioplasty (a procedure to open clogged coronary arteries); had a heart attack; or died. The scan detected high calcium deposits in 95 percent of the 224. Among those participants who didn't develop heart problems, the scans showed that 67 percent had low amounts of calcium deposits.
After a statistical analysis, the researchers concluded that the scans are not appropriate for people at high risk of heart attack who should be identified and treated based on other risk factors. Nor did they find scans appropriate for those at low risk. The problem is that scans don't tell you whether the calcium is in the lining of the arteries, where it is often associated with atherosclerosis and decreased blood flow, or whether it is in the muscular layer, where it may not be a problem. People with positive scans need further testing, usually a thallium stress test, to see whether blood flow to the heart is impaired.
However, the researchers did recommend scans to a group considered at "medium risk," those broadly identified as men over 45 and women over 50 with at least one cardiac risk factor besides age, such as diabetes, hypertension, high cholesterol, peripheral vascular disease, or a positive family history of heart disease. This recommendation was endorsed in an accompanying editorial as well as in a statement by the president of the American Heart Association.
The painless test takes about 10 minutes, and costs between $300 and $600, which usually is not reimbursed by health insurance. We still don't know whether patients who decide to have the scans and any follow-up tests and treatment recommended will do better than those who don't. Based on the study findings, I would suggest that you consult with your physician and assess your risks of heart disease before making a decision about having an EBCT scan.
Andrew Weil, M.D.